Nice, already in vertex form
y=a(x-h)^2+k
(h,k) is vertex
therfor since (-3,6) is vertex
we are looking for something like
y=a(x-(-3))^2+6 simplified to
y=a(x+3)^2+6
A is ansre
D shows equivalent expressions
1 is not a function. 2 is not. 3 is not. 4 and 5 are functions. 6 is not.